At present, an active-matrix liquid crystal display is widely used, and mainly comprises an array substrate, a color filter substrate and a liquid crystal molecule layer provided between the array substrate and the color filter substrate. As shown in FIG. 1, FIG. 2 and FIG. 3, the array substrate is provided with a plurality of pixel units, and each pixel unit comprises a thin film transistor 1 and a pixel electrode 20. The thin film transistor 1 serves as a switch for controlling the pixel electrode so as to determine whether a voltage is applied to the pixel electrode 20 or not and then determine whether the pixel unit displays or not. The thin film transistor 1 generally comprises a gate electrode 12, a gate insulating layer 13, an active layer 14, a source electrode 16, and a drain electrode 17, etc.
In a fabrication process of the array substrate, the source electrode 16 and the drain electrode 17 of the thin film transistor 1 are formed in a single patterning process, and a short circuit is apt to occur between the source electrode 16 and the drain electrode 17. In particular, in the case that a gray-tone or half-tone mask is used in the fabrication process of the array substrate to simultaneously form the source electrode 16, the drain electrode 17 and the active layer 14, the short circuit is more apt to occur between the source electrode 16 and the drain electrode 17.
In the case that the short circuit occurs between the source electrode 16 and the drain electrode 17 of the thin film transistor 1 in a certain pixel unit, a repair method is performed to cut off a portion where the source electrode 16 of the thin film transistor 1 is connected with a data line 15, so that the pixel unit becomes a dark spot. The above-described repair method will result in a decreased of the yield of the array substrate.